SV40, a known tumorigenic agent in rodents, was inoculated into humans as a contaminate ofkilled poliovirus vaccine in the 1950's. The oncogenic and teratogenic properties of this virus were studied in babies of rhesus monkeys, a natural host of SV40 virus. We found that the virus was teratogenic, producing hydrocephalus in several of the inoculated fetal monkeys. Animals were observed for 3 years and at termination of the study, no tumors were found. Group B streptococci (GBS) are an important cause of serious infection, often neurological, in human neonates. A method for early diagnosis of this in neonates is needed. Using the rhesus monkey model in which fetal monkeys were challenged with GBS, we were able to detect GBS antigen in amniotic or gastric aspirate fluid from all infected monkeys and their newborn by used of the Latex Particle Agglutination (LAP) test. Studies are now under way to use this LPA test to detect human infants at risk with GBS infections.